An automated microfluidic chip-top flow image cytometer and cell sorter has been developed that is capable of precisely distinguishing and directing both cells and colloidal particles This approach relies on the natural separation maintained by laminar microfluidic streams and the ability of applied fields, specifically optical manipulation techniques, to translate cells and particles between these streams These microdevices have the potential to perform chip-top microbiology more rapidly and with less associated hardware and preparation time than any other techniques currently available Furthermore, the optical actuation approach allows for seamless integration with widely applied fluorescence labeling and detection schemes Single chip-top devices that employ this technology will be capable precisely handling individual cells and microspheres and will be poised to make a considerable contribution to molecular biology on the nanoscale, and therefore molecular therapeutics in the coming decades The specific aims of this proposal include 1) The expansion of the existing cytometry configuration to accommodate multiple sorting fates by using an optical trap to precisely position particles and cells in channels and allowing laminar flows to direct them to the proper outlet channel 2) The integration of fluorescence based detection for rapid discrimination among cell phenotypes, binding events and particle-bound compounds 3) The increase of sorting rates through optimization of detection schemes, an increase in the number of simultaneous traps, and through parallelization of multiple devices upon the same chip 4) The realization of a working prototype capable of handling cells, performing multiple bead-based analyses and rapidly recovering and interpreting the results of these tests